1. Field of the Invention
The present invention relates to a coloring composition that contains a resin having a dye structure and is suitable for producing a color filter used for a liquid crystal display device or a solid-state imaging device, a colored pattern, a color filter and a method of producing the same, a pattern forming method, a solid-state imaging device, and an image display device.
2. Description of the Related Art
As one of the methods of producing a color filter used for a liquid crystal display device or a solid-state imaging device, there is a pigment dispersion method, and as the pigment dispersion method, there is a method of producing a color filter by photolithography by using a radiation-sensitive coloring composition that is obtained by dispersing pigments in various photosensitive compositions. Specifically, a radiation-sensitive coloring composition is coated onto a substrate by using a spin coater, a roll coater, or the like, followed by drying to form a coating film, and the coating film is developed by pattern exposure, thereby obtaining colored pixels. This operation is repeated for the number of the desired colors, thereby producing a color filter.
The above method is stable with respect to light or heat since the method uses pigments, and positional accuracy is sufficiently secured since patterning is performed by photolithography. Accordingly, the method has been widely used as a method suitable for producing a color filter or the like for color display.
Meanwhile, in recent years, there has been a demand for color filters for a solid-state imaging device such as a CCD to have a higher resolution. As the resolution of the color filter increases, the size of a pattern tends to be miniaturized, but it is considered that the pigment dispersion method that has been widely used in the related art has a difficulty in further improving resolution while also miniaturizing the size of a pattern. One of the reasons is that coarse particles generated due to the aggregation of pigment particles cause color unevenness in a fine pattern. Consequently, in recent years, the pigment dispersion method having been widely used so far has not necessarily been used for purposes requiring a fine pattern, such as in a solid-state imaging device.
In the related art, a color filter has been prepared using a pigment as a colorant, but recently, using a dye instead of a pigment has been examined. When a dye is used, the following points particularly become problems.
(1) A dye is generally inferior to a pigment in terms of light resistance and heat resistance. Particularly, there is a problem in that optical characteristics are changed due to a high-temperature process when a film is formed using ITO (indium tin oxide) widely used as an electrode of liquid crystal display or the like.
(2) Since a dye tends to suppress a radical polymerization reaction, in a system using radical polymerization as curing means, there is a difficulty in designing a radiation-sensitive coloring composition.
Particularly, when photolithography is used for preparing a color filter, the following points become problems.
(3) Generally, a dye exhibits low solubility in an aqueous alkaline solution or an organic solvent (hereinafter, simply referred to as a “solvent”), so it is difficult to obtain a radiation-sensitive coloring composition having a desired spectrum.
(4) A dye interacts with other components in a radiation-sensitive coloring composition in many cases, and it is difficult to adjust the solubility (developability) in an exposed and an unexposed portion.
(5) When a molar extinction coefficient (ε) of a dye is low, the dye has to be added in a large amount. As a result, amounts of other components in a radiation-sensitive coloring composition, such as a polymerizable compound (monomer), a binder, and a photopolymerization initiator, have to be relatively reduced, and curability of the composition, heat resistance after curing, developability, and the like deteriorate.
Due to these problems, it has been difficult so far to form a colored pattern that is constituted with a fine and thin film for a high-resolution color filter and that has excellent fastness by using a dye. In addition, in a case of a color filter for a solid-state imaging device, a coloring layer is required to be a thin film of 1 μm or less. Accordingly, in order to obtain desired absorption, a large amount of dye needs to be added to a radiation-sensitive coloring composition, and consequently, the problem described above arises.
Moreover, a fact that when a radiation-sensitive coloring composition containing a dye is formed into a film and then subjected to a heating treatment, a phenomenon of color migration is easily caused between different colors of colored patterns adjacent to each other or between layers laminated and stacked on each other has been observed. In addition to color migration, there is also a problem that a pattern is easily peeled off in an area with a low exposure amount due to decrease in sensitivity, a problem that since the amount of photosensitive components contributing to photolithography properties is relatively reduced, a desired shape or color density is not obtained due to heat sagging or elution at the time of development, or the like.
As a method for resolving these problems, there is a disclosure regarding a method of solving these problems by polymerizing dyes (for example, see JP2007-139906A, JP2007-138051A, JP3736221B, and JP2011-95732A)